618 



SCIENCE 



[N. S. Vol. XLIV. No. 1139 



SPECIAL ARTICLES 



THE ANALYSIS OF "DUST" COLLECTED IN A 



VACUUM CLEANER FROM THE BOOK 



SHELVES OF THE RENSSELAER 



POLYTECHNIC INSTITUTE 



LIBRARY 



Microscopical Examination. — Hair, green 

 wool, white wool, cotton fibers, fly wings, sand 

 grains, wood, paper, string, celluloid, pieces of 

 finger nails, metallic iron and leather. 



Life in water suspension of dust (microscopically 

 X 320), none. 



Qualitative examination: Iron, aluminum, sodium 

 and calcium. 



Volatile matter — 39.74 per cent. 



Ash — 60.26 per cent. 



Silica — 14.18 per cent, (hydrofluoric acid test). 



Total nitrogen — 1.01 per cent. (Kjeldahl method). 



Nitrogen as nitrates — .015 per cent, (color test). 



Nitrogen as nitrites — .0001 per cent, (color test). 



Chlorine as chlorides — .15 per cent, (equivalent to 

 .2485 per cent, of common salt). 



Total carbon — 15.9 per cent, (by combustion fur- 

 nace) . 



Nutrient jelly, total bacteria count (average of 6 

 plates) — 318,000 per gram. 



Lactose litmus agar, total count — 9,000 per gram. 



Bacillus coli communis — present (lactose bile). 



Bacteria counts were secured from one gram of 

 the dust shaken with sterile water. 



THE ANALYSIS OF LIBRARY DUST 



The floor of the library is of Torazzo and 

 the book shelves are made of sheet steel painted 

 with gray zinc paint. 



The microscopical examination of the dust 

 showed human hair and other hair probably 

 derived from soft hats. There were likewise 

 wool and cotton fibers from clothing, sand 

 from the mud tracked in on shoes and the 

 gradual pulverizing of the floor; fly wings 

 from dead flies and paper from book leaves. 

 The remaining articles present explain them- 

 selves. In a water suspension of this dust no 

 life could be detected with a lens magnifying 

 320 diameters. 



The elements found in the qualitative ex- 

 amination come chiefly from the wear and 

 tear of the floor and walls; the latter being 

 coated with plaster of Paris probably ac- 



counted for most of the calcium. Mud tracked 

 in would account for some of the iron and 

 aluminum present. The sodium found was 

 due to the wear of the floor as well as perspira- 

 tion from the handling of the books. Metallic 

 iron was furnished by the nails in shoes and 

 was removed from the dust by the use of 

 a magnet. 



The low per cent, of volatile matter, 39.74 

 per cent., is due to organic materials such as 

 wool, cotton, shoe leather and rubber heels. 

 The high ash, however, is accounted for by the 

 compounds of iron, aluminum, caleium and 

 silicon present as well as by the metallic iron 

 noted above. 



The total carbon content is high, but consid- 

 ering the amount of wool and cotton present 

 together with paper fiber, coal dust and smoke 

 from nearby chimneys and locomotives, this 

 amount can be readily understood. 



The chlorine is probably all present as 

 sodium chloride (common salt) which might 

 come, as stated above, from perspiration left 

 on the books and mud carried in on shoes. 



The total nitrogen is high, the nitrates and 

 nitrites low, hence the nitrogen must be pres- 

 ent almost entirely as nitrogenous organic ma- 

 terials such as hair and other fixed organic 

 compounds. 



The Bacillus coli communis was found. It 

 may come from several sources, the most prob- 

 able one being the hands while handling books. 

 The bacillus might also be present because of 

 the coughing, sneezing and possible expectora- 

 tion of people using the library. 



The total number of bacteria in the dust of 

 such a confined space as a library would nat- 

 urally be high, as the dust would catch the 

 bacteria and have a tendency to hold them. 



One of the chief points of interest connected 

 with this analysis is the presence of Bacillus 

 coli communis. "Where this organism survives, 

 more harmful bacteria might also remain, 

 such as those producing typhoid fever, chol- 

 era, diphtheria and especially tuberculosis, 

 which latter disease is caused by a bacillus 

 especially able to resist the sterilizing influ- 

 ence of drying. 



E. E. Eees 



